Perhaps more damaging was the revelation that Mr Ross had been accused of harassment and bullying by multiple women. Party president Peter Goodfellow knew about the alleged behaviour, yet Mr Ross was promoted to the front bench anyway.

Ahead of the weekly caucus meeting on Tuesday, Mr Bridges told media National was seeking independent advice on a review into the party's culture.

"A number of women have been affected here. I'm going to talk to Parliamentary Services this week to make sure women feel absolutely safe in the workplace."

Mr Bridges said he had also spoken to his deputy Paula Bennett over her comment that Mr Ross' conduct was inappropriate for a married man before his affairs were made public.

Newshub understands the findings probably won't be made public.

That same morning Newshub had asked several National MPs whether they thought such a review was necessary.

Deputy leader Paula Bennett said there was no need for an investigation and the party was united after the chaos of the last few days.

"There's a whole lot of things that went down last week that were pretty extraordinary," she told Newshub. "We're just going to get on with this week, and we wish [Mr Ross] well."

She denied that Mr Bridges' leadership was in question, but Newshub political editor Tova O'Brien says that's not true.

"Trust me, his MPs are talking about Simon Bridges' leadership and whether he can make it to 2020," she told The AM Show.

Waimakariri MP Matt Doocey declined to say whether there should be an internal investigation, but did make the comment that mental illness is something that devastates families.

Prime Minister Jacinda Ardern told Newstalk ZB that Parliament is a stressful environment that "needs to be better" at addressing mental health.

"I talk a lot about trying to do politics differently. We have stayed out of what has happened in the past week because of that belief, but we have a long way to go."

Nicky Wagner and Maureen Pugh, who were both the target of mean-spirited comments by Mr Bridges and Mr Ross in the audio released last week, told Newshub no investigation was needed.

When asked how Mr Ross' alleged behaviour went unchecked for so long, Ms Pugh said: "I guess that's why he's now getting the help he needs."